Mice have 16 teeth that grow throughout their lives. Domesticated fancy mice, though they are generally considered nonaggressive and tolerant, can bite out of fear, hostility or unfamiliarity. If you have a concern that a pet mouse may bite, approach and pet the mouse with a cotton swab until a trusting human-rodent bond forms.
Proper Mouse Handling
Small children can sometimes have a heavy hand when caressing mice, and this has the potential to antagonize a mouse to fear, leading to a bite. Mice do not possess the strongest eyesight, so a surprise approach or grab without notice may startle one and incite a bite. Never pick up a mouse by the tail, as this action could hurt and scare it. You could get bit. Make sure they see you approach and pick them up by scooping under their bellies.
If a Mouse Bites
Should a mouse bite, it is important not to become angry with him or to shake the mouse from your hand to shoo him away. Instead, stop whatever action brought the bite about, and avoid stressing the mouse further. Gently stroke the mouse with the back of a finger to soothe the critter. Work to build a trusting relationship with the pet mouse through routinely cleaning the animal's cage, moving around slowly inside and speaking quietly. Bonding with young mice like this reduces the likelihood of biting as they mature.